Cutter inserts for drill bits for use in boring into the earth may comprise a layer of polycrystalline diamond (PCD) bonded to a cemented carbide substrate. Such cutter inserts may be referred to as polycrystalline diamond compacts (PDC).
PCD is an example of a superhard, also called superabrasive, material comprising a mass of substantially inter-grown diamond grains, forming a skeletal mass defining interstices between the diamond grains. PCD material comprises at least about 80 volume % of diamond and may be made by subjecting an aggregated mass of diamond grains to an ultra-high pressure of greater than about 5 GPa and temperature of at least about 1,200 degrees centigrade in the presence of a sintering aid.
Suitable sintering aids for PCD may also be referred to as a catalyst material for diamond. Catalyst material for diamond is understood to be material that is capable of promoting direct inter-growth of diamond grains at a pressure and temperature condition at which diamond is thermodynamically more stable than graphite. Some catalyst materials for diamond may promote the conversion of diamond to graphite at ambient pressure, particularly at elevated temperatures. Examples of catalyst materials for diamond are cobalt, iron, nickel and certain alloys including any of these. PCD may be formed on a cobalt-cemented tungsten carbide substrate, which may provide a source of cobalt catalyst material for the PCD. The interstices with PCD may be at least partly be filled with a material, which may be referred to as a binder or a filler material. In particular the interstices may be wholly or partially filled with catalyst material for diamond.
Components comprising PCD are used in a wide variety of tools for cutting, machining, drilling or degrading hard or abrasive materials such as rock, metal, ceramics, composites and wood-containing materials. For example, PCD bodies are commonly used as cutter inserts on drill bits used for boring into the earth in the oil and gas drilling industry. PCD bodies are also used for machining and milling metal-containing bodies, such as may be used in the auto manufacturing industry. In many of these applications the temperature of the PCD material becomes elevated as it engages a rock formation, workpiece or body with high energy.
PCD is extremely hard and abrasion resistant, which is the reason it is the preferred tool material in some of the most extreme machining and drilling conditions, and where high productivity is required. A disadvantage of PCD containing certain catalyst materials for diamond as a filler material may be its relatively poor thermal stability above about 400 degrees centigrade. The catalyst material may promote the degradation of the PCD at elevated temperature, particularly at temperatures greater than about 750 degrees centigrade, as may be experienced in manufacture and use of PCD compacts.
U.S. Pat. No. 7,377,341 discloses thermally stable ultra-hard compact constructions comprising a body formed from an ultra-hard material such as PCD, including a thermally stable region positioned adjacent a working surface of the body. The ultra-hard material body can be attached to a desired substrate, thereby forming a compact, and an intermediate material can be interposed between the substrate and the body. The intermediate material may be one that does not infiltrate into the ultra-hard material body during high pressure/high temperature processing and that can operate as a barrier to prevent migration of constituent materials from the substrate to the ultra-hard material body.
U.S. Pat. No. 7,473,287 discloses thermally-stable polycrystalline diamond materials comprising a first material phase that includes a plurality of bonded together diamond crystals, and a second material phase that includes a reaction product formed between a binder/catalyst material used to facilitate diamond crystal bonding and a material that is reactive with the binder/catalyst material. A barrier layer may be placed between PCD material and a substrate to prevent unwanted infiltration of extra cobalt therein which could adversely impact the thermal stability of the resultant PCD material.
United States patent application publication number 2007/0079994 discloses thermally stable diamond-bonded compacts that include a diamond-bonded body comprising a thermally stable region that extends a distance below a diamond-bonded body surface. The thermally stable region has a material microstructure comprising a matrix first phase of bonded together diamond crystals, and a second phase interposed within the matrix first phase. The second phase comprises one or more reaction products formed between one or more infiltrant material and the diamond crystals at high pressure/high temperature (HPHT) conditions. The infiltrant or replacement material may include one or more of the following elements: Si, Cu, Sn, Zn, Ag, Au, Ti, Cd, Al, Mg, Ga, Ge, which may also be used in compounds containing conventional solvent-catalyst materials (transition metals) where the solvent catalyst is rendered inactive by reaction with another material.
United States patent application publication number 2008/0115421 discloses a method of fabricating a superabrasive article, in which at least a portion of interstitial regions of a pre-sintered-polycrystalline-diamond body may be infiltrated with silicon from a silicon-containing material. At least a portion of metal-solvent catalyst located within the at least a portion of interstitial regions of the pre-sintered-polycrystalline-diamond body may be displaced into a porous mass. The silicon and the pre-sintered-polycrystalline-diamond body are reacted to form silicon carbide within the at least a portion of the interstitial regions.
There is a need to provide a polycrystalline diamond (PCD) element having enhanced thermal stability. There is also a need to provide a PCD element having enhanced thermal stability combined with enhanced resistance to fracture.